Electrically driven dump truck

ABSTRACT

A vehicle control device  50 , a controller  100 , an inverter control device  30  and a steering control device  32  constitute a control device  200  which executes control to give a yaw moment to a vehicle  1  to make the vehicle  1  travel while tracing a trolley wire  3 R,  3 L based on image information detected by a camera  15 . The control device  200  converts an image acquired by the camera  15  into coordinate information, calculates at least one representative point of the vehicle  1  and at least one target point situated on the trolley wire  3 R,  3 L based on the coordinate information, and executes the control to give a yaw moment to the vehicle  1  so that the representative point approaches the target point. With this configuration, an electrically driven dump truck capable of lightening the operating load on the driver during the trolley traveling is provided.

TECHNICAL FIELD

The present invention relates to an electrically driven dump truck. Inparticular, to an electrically driven dump truck which travels by usingelectric power from trolley wires.

BACKGROUND ART

Some types of dump trucks that travel in mines are known as the serieshybrid type. Such series hybrid type dump trucks generate electric powerwith a generator driven by the engine and supply the electric power torear wheel motors for driving the rear wheels. By taking advantage ofthe electrical configuration of the series hybrid type, travelingtechnology based on the trolley system has been implemented. In thetrolley-based traveling technology, trolley wires generally employed forelectric trains are installed in prescribed climbing sections. In theclimbing sections with trolley wires, a vehicle having power collectors(provided on the vehicle to be movable up and down) travels not by usingthe electric power supplied by the engine and the generator but by usingelectric power acquired from the trolley wires by elevating sliders ofthe power collectors to be in contact with the trolley wires(hereinafter referred to as “trolley traveling”). An example of thetrolley-based traveling technology has been described in PatentLiterature 1, for example. In this case, the drop in the traveling speedin the climbing sections (equipped with the trolley wires enabling thetrolley traveling) can be avoided since the electric power supplied fromthe trolley wires is greater than the electric power generated with theengine power.

Meanwhile, there exists a conventional technology detecting the lane(for the traveling of the vehicle) and controlling the vehicle toprevent the vehicle from deviating from the lane based on the result ofthe detection, as described in Patent Literature 2. This technology ispertinent to the traveling technology of automobiles. Images of the roadsurface are shot with a camera or the like and lane markers (whitelines, Botts dots, etc.) corresponding to the lane are extracted fromthe images by image processing. The control of the vehicle is executedby adjusting the steering and the driving/braking force so that thevehicle travels between the extracted lane markers. Imaginary offsetlane markers are set a prescribed distance inside the lane markers (areato be judged as the lane) exclusively in prescribed sections, and acontrol value is increased as the vehicle deviates outward from the lanemarker.

PRIOR ART LITERATURE Patent Literature

-   -   Patent Literature 1: U.S. Pat. No. 4,483,148    -   Patent Literature 2: JP-11-96497-A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In the trolley-based traveling technology like the one described in thePatent Literature 1, the driver of the vehicle (dump truck) judgeswhether or not the vehicle has entered a trolley traveling section. Whenthe vehicle has entered a trolley traveling section and the driverviewing the positional relationship between the sliders and the trolleywires judges that the sliders are capable of contacting the trolleywires, the driver operates a switch (e.g., trolley traveling startingbutton), by which the trolley traveling is started. During the trolleytraveling, the driver visually checks the vehicle's displacement withrespect to the trolley wires and performs the steering operation so thatcentral positions of the sliders do not deviate widely from the trolleywires in the lateral direction. The timing for ending the trolleytraveling is also judged by the driver; the trolley traveling is endedin response to the driver's pressing a button, for example.

However, such operations based on visual checks by the driver put aheavy load on the driver during the trolley traveling.

The traveling control technology described in the Patent Literature 2 iscapable of controlling the vehicle (automobile) to prevent the vehiclefrom deviating from the lane. However, the lane markers on ordinaryroads (like those described in the Patent Literature 2) do not exist onroad surfaces in mines where dump trucks are traveling. Further, thecondition of the road surface changes every hour and it is difficult todetect a suitable area on the road surface for the traveling by means ofa sensor (e.g., radar) and image processing according to theconventional technology.

It is therefore the primary object of the present invention to providean electrically driven dump truck capable of lightening the operatingload on the driver during the trolley traveling.

Means for Solving the Problem

To achieve the above object, an invention described in claim 1 providesan electrically driven dump truck which elevates a slider of a powercollector provided on a vehicle to be movable up and down, places theslider in contact with a trolley wire installed along a lane, andtravels by using electric power from the trolley wire, comprising: atrolley wire detecting device which is provided on the vehicle anddetects the trolley wire from below when the dump truck is traveling;and a control device which executes control to give a yaw moment to thevehicle so that the vehicle travels while tracing the trolley wire basedon information detected by the trolley wire detecting device.

In the electrically driven dump truck configured as above, the trolleywire is detected from below with the trolley wire detecting device, andthus there are less factors leading to detection errors compared to theconventional technique detecting lane markers, etc. by capturing imagesof the ground surface. As a result, the accuracy of the trolley wiredetection is improved. Thanks to the improvement of the trolley wiredetection accuracy, the control accuracy of the control to give a yawmoment to the vehicle so that the vehicle travels while tracing thetrolley wire is improved and the central position of the slider of thetraveling vehicle hardly deviates widely from the trolley wire in thelateral direction. Consequently, the operating load on the driver duringthe trolley traveling can be lightened considerably.

In an invention described in claim 2, in the electrically driven dumptruck according to claim 1, the control device converts an imageacquired by the camera into coordinate information, calculates at leastone representative point of the vehicle and at least one target pointsituated on the trolley wire based on the coordinate information, andexecutes control to give a yaw moment to the vehicle so that therepresentative point approaches the target point.

With this configuration, the vehicle is controlled to travel whiletracing the trolley wire.

In an invention described in claim 3, in the electrically driven dumptruck according to claim 1, the control device calculates inclination ofthe vehicle with respect to the trolley wire based on the coordinateinformation and executes control to give a yaw moment to the vehicle sothat the inclination decreases.

With this configuration, the vehicle is controlled to travel whiletracing the trolley wire.

In an invention described in claim 4, in the electrically driven dumptruck according to claim 2, the control device calculates a deviationbetween the representative point and the target point and executes thecontrol to give a yaw moment to the vehicle so that the representativepoint approaches the target point when the absolute value of thedeviation is greater than a first threshold value.

With this configuration, the frequency of operation of devices executingthe yaw moment control can be reduced and high control stability andriding comfort can be secured.

In an invention described in claim 5, in the electrically driven dumptruck according to claim 4, the control device increases the yaw momentgiven to the vehicle with the increase in the absolute value of thedeviation when the absolute value is greater than the first thresholdvalue.

With this configuration, the vehicle is given the yaw moment so that thetrolley wire quickly returns to the center of the slider when the sliderof the traveling vehicle is about to widely deviate from the trolleywire in the lateral direction. Consequently, the dump truck can securelybe prevented from deviating from the lane with the trolley wire.

In an invention described in claim 6, in the electrically driven dumptruck according to claim 2, the control device issues a warning that thevehicle is apt to deviate from the lane when the absolute value of thedeviation is greater than a second threshold value.

With this configuration, it becomes possible to urge the driver tocorrect the steering.

In an invention described in claim 7, the electrically driven dump truckaccording to any one of claims 1-6 further comprises right and leftelectric motors for traveling. The control device executes both thecontrol to give a yaw moment to the vehicle and traveling speed controlby controlling the right and left electric motors.

With this configuration, efficient control, achieving both thedeceleration and the generation of the yaw moment at the same time, canbe carried out by the control of the electric motors.

In an invention described in claim 8, the electrically driven dump truckaccording to any one of claims 1-6 further comprises right and leftelectric motors for traveling and a steering device. The control deviceincludes a vehicle control device, a controller, an inverter controldevice and a steering control device. The vehicle control devicecalculates a yaw moment correction value, for the control to give a yawmoment to the vehicle so that the vehicle travels while tracing thetrolley wire, based on image information acquired by the camera. Thecontroller controls at least the right and left electric motors or thesteering device by using the inverter control device and/or the steeringcontrol device based on the yaw moment correction value.

By executing the yaw moment control by using the vehicle control deviceand the controller as separate components as described above, even whenthe controller is an already-existing controller, the yaw moment controlin accordance with the present invention can be carried out by justadding the vehicle control device to the controller. The parameters ofthe yaw moment control can be adjusted just by changing the functions ofthe vehicle control device. Consequently, high flexibility can be givento the control system.

In an invention described in claim 9, in the electrically driven dumptruck according to any one of claims 1-8, the trolley wire detectingdevice includes: a camera which is provided on the vehicle andcontinuously captures images of the trolley wire when the dump truck istraveling; and an illuminating device which is provided on the vehicleand illuminates the trolley wire.

Even when a camera is employed for the trolley wire detecting device asabove, illuminating the trolley wire with the illuminating device keepshigh contrast between the sky and the trolley wire. Consequently, yawmoment control with which the vehicle travels while tracing the trolleywire can be executed with high accuracy not only in the daytime withfine weather but also in conditions in which such high contrast betweenthe sky and the trolley wire is hardly achieved (evening, nighttime,rainy weather, etc.).

Effect of the Invention

According to the present invention, the trolley wire is detected frombelow with the trolley wire detecting device, and thus there are lessfactors leading to detection errors compared to the conventionaltechnique detecting lane markers, etc. by capturing images of the groundsurface. As a result, the accuracy of the trolley wire detection isimproved. Thanks to the improvement of the trolley wire detectionaccuracy, the control accuracy of the control to give a yaw moment tothe vehicle so that the vehicle travels while tracing the trolley wireis improved and the central position of the slider of the travelingvehicle hardly deviates widely from the trolley wire in the lateraldirection. Consequently, the operating load on the driver during thetrolley traveling can be lightened considerably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing the external appearance of an electricallydriven dump truck in accordance with an embodiment of the presentinvention.

FIG. 2 is a rear view showing the external appearance of the dump truck.

FIG. 3 is a schematic block diagram showing a drive system of theelectrically driven dump truck in this embodiment.

FIG. 4 is a schematic diagram showing the configuration of powercollectors for receiving electric power from trolley wires.

FIG. 5 is a schematic diagram showing a steering system which is made upof a steering control device and a steering device.

FIG. 6 is a block diagram showing a function of the steering controldevice for calculating a steerage torque command value.

FIG. 7 is a block diagram for explaining a function of a vehicle speedcontrol unit of a controller.

FIG. 8 is a block diagram showing the details of a function of a yawmoment control unit of the controller.

FIG. 9 is a graph showing the effect of a method implementing a yawmoment correction value by a driving force difference on the totaldriving force of the motors when the vehicle is traveling with its 100%motor driving force.

FIG. 10 is a schematic diagram showing an example of a method forcalculating motor torque command values.

FIG. 11 is a schematic diagram showing the configuration of a vehiclecontrol device and the input-output relationship between the vehiclecontrol device and the controller.

FIG. 12 is a schematic diagram showing the positional relationshipbetween the vehicle and an imaging area (detection area by trolley wiredetecting device) of a camera viewed from the side of the vehicle.

FIG. 13 is a schematic diagram showing the positional relationshipbetween the vehicle and the imaging area (detection area by trolley wiredetecting device) of the camera viewed from above (above the vehicle).

FIG. 14 is a schematic diagram showing an image captured by the camera.

FIG. 15 is a schematic diagram showing a process (edge extraction)performed on the captured image.

FIG. 16 is a schematic diagram showing a process (center lineextraction) performed on the captured image.

FIG. 17 is a schematic diagram showing a camera image captured when thevehicle has shifted to the left with respect to the trolley wires.

FIG. 18 is a schematic diagram showing a camera image captured when thevehicle is traveling obliquely to the trolley wires.

FIG. 19 is a block diagram showing the details of a function of avehicle state quantity control unit (flow of calculation for convertingdeviation between a present position and a target position into the yawmoment correction value).

FIG. 20 is a schematic diagram showing a trolley wire detecting area anda coordinate system used in another embodiment of the vehicle controldevice.

FIG. 21 is a flow chart showing a process flow from upward shooting withthe camera to control output in accordance with the other embodiment ofthe vehicle control device.

FIG. 22 is a schematic diagram similar to FIG. 20, showing the trolleywire detecting area and the coordinate system when a first thresholdvalue has been set.

FIG. 23A is a schematic diagram showing an example of a method forcalculating the yaw moment correction value corresponding to theposition of a target point.

FIG. 23B is a block diagram similar to FIG. 19, showing an example of amethod for calculating the yaw moment correction value corresponding tothe position of the target point.

FIG. 24 is a schematic diagram similar to FIGS. 20 and 22, showing thetrolley wire detecting area and the coordinate system when first andsecond threshold values have been set.

FIG. 25 is a flow chart showing another example of a trolley wiretracing control step in the flow chart of FIG. 21.

FIG. 26 is a schematic diagram showing an example of a method forcalculating a target vehicle speed correction value (for correcting thetarget vehicle speed to the decreasing side) depending on the positionof the target point.

FIG. 27 is a schematic diagram showing an example of a method forcalculating the target vehicle speed correction value (for correctingthe target vehicle speed to the increasing side) depending on theposition of the target point.

FIG. 28 is a schematic diagram similar to FIG. 10, showing a method forgenerating motor torque according to the target vehicle speed correctionvalue.

FIG. 29 is a schematic diagram showing a hysteresis process which can beexecuted instead of a counter process for preventing hunting ofjudgment.

FIG. 30 is a schematic diagram similar to FIG. 12, showing an example inwhich the shooting direction of the camera is shifted forward.

MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, a description will be given in detail ofa preferred embodiment in accordance with the present invention.

<Configuration of Vehicle—Dump Truck>

FIG. 1 is a side view showing the external appearance of an electricallydriven dump truck in accordance with an embodiment of the presentinvention.

In FIG. 1, the dump truck comprises a vehicle 1, a vessel 2 for carryingearth, sand, etc., right and left power collectors 4R and 4L forcollecting electric power, and right and left rear wheels (tires) 5R and5L driven by the electric power collected by the power collectors 4R and4L. The right and left power collectors 4R and 4L are equipped withsliders 4Ra and 4La which are movable up and down to receive theelectric power from two (right and left) trolley wires 3R and 3L. One ofthe trolley wires 3R and 3L is at a high voltage and the other isgrounded. The power collectors 4R and 4L are provided on a front part ofthe vehicle 1. The dump truck is equipped with a trolley wire detectingdevice 15 mounted on the front part of the vehicle 1. The trolley wiredetecting device 15 continuously detects the trolley wires 3R and 3L infront of the dump truck when the dump truck is traveling. The trolleywire detecting device 15 is a device newly mounted on the dump truckaccording to the present invention. While the trolley wire detectingdevice 15 is mounted on the front part of the vehicle 1 in theillustrated example, the trolley wire detecting device 15 may also bearranged differently (e.g., on the roof of the vehicle 1).

FIG. 2 is a rear view showing the external appearance of the dump truck.Each rear wheel 5R, 5L is formed as a double-tire wheel to endure theload of earth, sand, etc. loaded on the vessel 2. The right and leftdouble-tire wheels 5R and 5L are driven and braked by right and leftelectric motors 6R and 6L (e.g., induction motors).

FIG. 3 shows a drive system of the electrically driven dump truck ofthis embodiment.

In FIG. 3, the drive system of the electrically driven dump truckincludes an accelerator pedal 11, a retarder pedal 12, a shift lever 13,a combined sensor 14, an engine 21, an AC generator 22, the other engineload 28, a rectifier circuit 23, a sensing resistor 24, a capacitor 25,a chopper circuit 26, a grid resistor 27, the power collectors 4R and4L, the rear wheels 5R and 5L, the electric motors 6R and 6L,decelerators 7R and 7L, electromagnetic pickup sensors 16R and 16L, anda control device 200. The combined sensor 14 is used for sensing theforward/backward acceleration, the lateral acceleration and the yawrate. The decelerators 7R and 7L are connected to output shafts 6Ra and6La of the electric motors 6R and 6L, respectively.

The control device 200 includes an inverter control device 30, anelevation control device 31, a steering control device 32, a vehiclecontrol device 50 and a controller 100. The inverter control device 30controls the electric motors 6R and 6L according to torque commandsinputted thereto. The elevation control device 31 moves the sliders 4Raand 4La of the power collectors 4R and 4L up and down according tobutton operations by the driver or inputs from the outside. The steeringcontrol device 32 converts the driver's steering operation into anelectric signal and thereby controls the steering of the front wheels.The vehicle control device 50 is a characteristic part of the presentinvention.

The inverter control device 30 includes a torque command calculationunit 30 a, a motor control calculation unit 30 b and an inverter(switching element) 30 c (publicly-known configuration) for each of theright and left electric motors 6R and 6L. The power collectors 4R and 4Lare equipped with elevators which move the sliders 4Ra and 4La up anddown according to elevation command signals from the elevation controldevice 31. The details of the power collectors 4R and 4L, the elevationcontrol device 31, the steering system (including the steering controldevice 32) and the vehicle control device 50 will be described later.

<Basic Operation Including Traveling>

The depressing level P (the degree of depressing) of the acceleratorpedal 11 and the depressing level Q of the retarder pedal 12 areinputted to the controller 100 as signals for controlling the magnitudeof the driving force and the retarding force (braking force),respectively. For example, when the driver depresses the acceleratorpedal 11 to move the dump truck forward or backward, the controller 100outputs a command regarding a target revolution speed Nr to the engine21. The command regarding the target revolution speed Nr is outputtedbased on a preset table of target revolution speeds Nr corresponding tovarious accelerator angles. The engine 21 is a diesel engine equippedwith an electronic governor 21 a. Upon receiving the command regardingthe target revolution speed Nr, the electronic governor 21 a controlsthe fuel injection quantity so that the engine 21 revolves at the targetrevolution speed Nr.

The AC generator 22 is connected to the engine 21 to generate AC power.The electric power generated by the AC power generation is rectified bythe rectifier circuit 23 and stored in the capacitor 25 (DC voltage: V).A voltage value detected by the sensing resistor 24 (dividing the DCvoltage V at a certain ratio) is fed back to the controller 100. The ACgenerator 22 is controlled by the controller 100 receiving the feedbackso that the voltage value equals a prescribed constant voltage V0.

The electric power generated by the AC generator 22 is supplied to theright and left electric motors 6R and 6L via the inverter control device30. The controller 100 controls the supply of the necessary electricpower to the electric motors 6R and 6L by controlling the AC generator22 so that the DC voltage V acquired by the rectification by therectifier circuit 23 equals the prescribed constant voltage V0. Incontrast, when the sliders 4Ra and 4La of the power collectors 4R and 4Lare in contact with the trolley wires 3R and 3L, the DC voltage V0 isdirectly supplied from the trolley wires 3R and 3L to the invertercontrol device 30.

The controller 100 calculates torque command values T_MR_a and T_ML_acorresponding to the operation amounts of the accelerator pedal 11 andthe retarder pedal 12 and then generates and outputs torque commandvalues T_MR and T_ML for the right and left electric motors 6R and 6Lbased on the torque command values T_MR_a and T_ML_a, torque commandvalues T_MR_V and T_ML_V for vehicle speed control, and motor torquecorrection values T_MR_Y and T_ML_Y for yaw moment control (explainedlater). The torque command values T_MR and T_ML for the right and leftelectric motors 6R and 6L and the revolution speeds ωR and ωL of theelectric motors 6R and 6L detected by the electromagnetic pickups 16Rand 16L are inputted to the inverter control device 30. The invertercontrol device 30 drives each of the electric motors 6R and 6L via thetorque command calculation unit 30 a, the motor control calculation unit30 b and the inverter (switching element) 30 c.

The right and left rear wheels (tires) 5R and 5L are connected to theelectric motors 6R and 6L via the decelerators 7R and 7L, respectively.Each electromagnetic pickup 16R, 16L is generally implemented by asensor which detects the peripheral speed of a cog of a gear inside thedecelerator 7R, 7L. In the drive system for the right-hand side, forexample, it is also possible to attach a gear for the detection to adrive shaft inside the electric motor 6R or to a drive shaft connectingthe decelerator 7R to the wheel (tire) 5R and arrange theelectromagnetic pickup 16R at the position of the gear.

When the driver of the traveling dump truck returns the acceleratorpedal 11 and depresses the retarder pedal 12, the controller 100executes control so that the AC generator 22 does not generate electricpower. Further, the torque command values T_MR_a and T_ML_a from thecontroller 100 turn negative and thus the inverter control device 30drives the electric motors 6R and 6L to give braking force to thetraveling dump truck. In this case, the electric motors 6R and 6Lfunction as generators so as to electrically charge the capacitor 25 byuse of the rectification function of the inverter control device 30. Thechopper circuit 26 operates to keep the DC voltage value V within apreset DC voltage value V1 while converting electric energy to thermalenergy by feeding electric current to the grid resistor 27.

<Upward/Downward Movement of Sliders of Power Collectors>

Next, the elevators for the sliders 4Ra and 4La of the power collectors4R and 4L will be explained below. FIG. 4 shows the configuration of thepower collectors 4R and 4L for receiving the electric power from thetrolley wires 3R and 3L. Since the power collectors 4R and 4L areidentical with each other in the configuration, the configuration of thepower collector 4L will be explained as a representative. The powercollector 4L has a hydraulic piston device 4 a as the elevator. Thehousing of the hydraulic piston device 4 a is fixed on the vehicle 1.The slider 4La is attached to an end of a rod 4 c of a hydraulic piston4 b of the hydraulic piston device 4 a. The contact/detachment of theslider 4La to/from the trolley wire 3L is controlled by verticallymoving the hydraulic piston 4 b with hydraulic fluid supplied from ahydraulic device 4 e (including a hydraulic pump) via a hydraulic line 4d. The slider 4La and the rod 4 c of the hydraulic piston 4 b areelectrically insulated from each other by an insulator 4 f. The electricpower of the trolley wire 3L is supplied to a power supply system of theinverter control device 30 (for driving the motors, see FIG. 3) via theslider 4La and an electric wire 4 g. The elevation control device 31 isconfigured to send the elevation command signal 4 h to the hydraulicdevice 4 e according to the driver's operation on an elevation switch ora switching (flag) operation or a control command signal from theoutside (e.g., the vehicle control device 50 of the present invention).While the elevator for the slider 4La is implemented by the hydraulicpiston device 4 a in this embodiment, the elevator may of course beimplemented by the system called “pantograph” by use of parallellinkage, spring, motor, etc. as is generally employed for electrictrains.

<Steering System>

Next, the steering system will be explained below by referring to FIG.5.

The steering system is made up of the aforementioned steering controldevice 32 and a steering device 40. The steering device 40 includes asteering wheel 41, a reaction force motor 42 having a steering anglesensor, a steerage motor 43 having a steerage angle sensor, and arack-and-pinion gear 44.

When the driver operates the steering wheel 41, the steering anglesensor of the reaction force motor 42 detects the operation amount ofthe steering wheel 41 and sends the detected operation amount to thesteering control device 32. The steering control device 32 sends atorque signal to the steerage motor 43 having the steerage angle sensorso that the present steerage angle equals a steerage angle correspondingto the steering angle of the driver. Front wheels 45R and 45L are turned(steerage) by steerage torque which is generated by the steerage motor43 and transmitted via the rack-and-pinion gear 44. Depending on themagnitude of this torque, reaction force torque is transmitted to thereaction force motor 42 having the steering angle sensor, by whichreaction force is transmitted to the steering wheel 41. At the sametime, the steering control device 32 sends the steering angle to thecontroller 100. The steering control device 32 has a function ofreceiving a steerage torque correction value from the controller 100 andoperating the steerage motor 43 (having the steerage angle sensor)according to the received steerage torque correction value. Whether thesteering control device 32 similarly sends the reaction force torque tothe reaction force motor 42 having the steering angle sensor or not canbe changed properly based on the mode (explained later) at that time anda command from the controller 100. For example, if the steering controldevice 32 receiving the steerage torque correction value from thecontroller 100 operates the steerage motor 43 having the steerage anglesensor according to the correction value without sending the reactionforce command value to the reaction force motor 42 having the steeringangle sensor, the driver loses the steering feeling at that moment eventhough the vehicle (dump truck) turns according to the steering angle.In contrast, if no command is sent to the steerage motor 43 having thesteerage angle sensor even with the steering operation by the driver,the vehicle (dump truck) does not turn in spite of the turning of thesteering wheel 41. This means is effective when the controller 100judges that the steering wheel 41 should not be operated for somereason, for example. As means for informing the driver that the steeringwheel 41 should not be operated at the moment, the steering controldevice 32 may generate torque in a direction opposite to the directionof the driver's operation on the steering wheel 41. The torque makes thedriver feel that the steering wheel 41 is heavy and recognize that thesteering wheel 41 should not be operated in the direction.

While the steer-by-wire system in which the steering wheel 41 is notdirectly linked to the front wheels 45R and 45L has been explained inthis embodiment, the steering system is not limited thereto. Forexample, an electric power steering system in which the reaction forcemotor 42 having the steering angle sensor and the steerage motor 43having the steerage angle sensor are directly connected together as anintegral component may also be employed. Further, the steerage motor 43having the steerage angle sensor may also be implemented by a motor ofthe hydraulic servo type. Furthermore, the correction value sent fromthe controller 100 may also be a corrected angle instead of the torque.In this case, the steering control device 32 may be configured toperform torque feedback control so as to eliminate the deviation betweenthe angle detected by the steerage angle sensor and the corrected angle.

FIG. 6 is a block diagram showing a function of the steering controldevice 32 for calculating a steerage torque command value. A conversionunit 32 a of the steering control device 32 converts the driver'ssteering angle received from the reaction force motor 42 having thesteering angle sensor into a driver steerage angle by multiplying thedriver's steering angle by a gain factor. A calculation unit 32 bsubtracts the present steerage angle from the driver steerage angle. Aconversion unit 32 c converts the subtraction result intodriver-requesting steerage torque by multiplying the subtraction resultby a gain factor. Then, a calculation unit 32 d calculates the steeragetorque command value by adding the steerage torque correction value(received from the controller 100) to the driver-requesting steeragetorque. The calculated steerage torque command value is outputted to thesteerage motor 43 having the steerage angle sensor.

<Vehicle Speed Control>

Referring again to FIG. 3, the controller 100 includes a vehicle speedcontrol unit 101. When a vehicle speed control mode has been selected,the vehicle speed control unit 101 implements the control of the vehiclespeed according to the vehicle speed control mode, by executing feedbackcontrol to the present vehicle speed with respect to a target vehiclespeed that is set in the vehicle speed control mode. FIG. 7 is a blockdiagram for explaining the function of the vehicle speed control unit101. As shown in FIG. 7, when the vehicle speed control mode is ON (1),that is, when a switch unit 101 c is at its ON position, the vehiclespeed control unit 101 receiving the target vehicle speed and thepresent vehicle speed calculates the difference between the two vehiclespeeds with a calculation unit 101 a, calculates the torque commandvalues T_MR_V and T_ML_V (for changing the present vehicle speed to thetarget vehicle speed) with a conversion unit 101 b by multiplying thedifference by a gain factor, and outputs the calculated torque commandvalues T_MR_V and T_ML_V. The vehicle speed control unit 101 receivesrevolution speeds ωR and ωL of the electric motors 6R and 6L detected bythe electromagnetic pickups 16R and 16L and calculates the vehicle speedfrom the revolution speeds. A command specifying whether or not to shiftto the vehicle speed control mode may be issued according to thedriver's operation on a switch of the vehicle control device 50 oraccording to an input from the outside, for example. The cancellation ofthe vehicle speed control mode may be made according to the driver'sdepressing the retarder pedal 12 or according to an input from theoutside. When the vehicle speed control mode is canceled, the command ofthe vehicle speed control mode is turned OFF (0) (i.e., the switch unit101 c is turned OFF) and a vehicle control torque command value 0 isoutputted by a zero output unit 101 d. The controller 100, having apreset table of engine revolution speed command values corresponding tovarious torque command values T_MR_V and T_ML_V, outputs an enginerevolution speed command value to the engine 21 based on the table.

<Yaw Moment Control>

As shown in FIG. 3, the controller 100 further includes a yaw momentcontrol unit 102 for controlling the turning direction of the vehicle.FIG. 8 is a block diagram showing the details of the function of the yawmoment control unit 102. As shown in FIG. 8, input signals to the yawmoment control unit 102 include, for example, a yaw moment control valuewhich is generated by other yaw moment control (e.g., sideslipprevention control), a yaw moment correction value which is generatedaccording to the present invention, the vehicle speed, theforward/backward acceleration, the lateral acceleration, the yaw rate,the steering angle, and a command of a yaw moment control mode. Outputsignals from the yaw moment control unit 102 are the steerage torquecorrection value and the torque correction values T_MR_Y and T_ML_Y forthe motors. The yaw moment control value and the yaw moment correctionvalue are added together by a calculation unit 102 a to determine a yawmoment command value. The yaw moment command value is inputted to asteering torque control unit 102 b, a motor torque control unit 102 cand an optimum distribution control unit 102 d. The steering torquecontrol unit 102 b calculates a steerage torque correction value basedon the inputted yaw moment command value. The motor torque control unit102 c calculates motor torque correction values based on the inputtedyaw moment command value. The optimum distribution control unit 102 dcalculates a yaw moment distribution ratio based on the yaw momentcommand value, the vehicle speed, the yaw rate, the steering angle, theforward/backward acceleration and the lateral acceleration inputtedthereto and then calculates a steerage torque correction value and motortorque correction values corresponding to the yaw moment distributionratio. The command of the yaw moment control mode is inputted to aswitch unit 102 e. When the yaw moment control mode is mode 1, theswitch unit 102 e outputs the steerage torque correction valuecalculated by the steering torque control unit 102 b. When the yawmoment control mode is mode 2, the switch unit 102 e outputs the motortorque correction value calculated by the motor torque control unit 102c. When the yaw moment control mode is mode 3, the switch unit 102 eoutputs the steerage torque correction value and the torque correctionvalues for the right and left motors calculated by the optimumdistribution control unit 102 d.

<Setting of Yaw Moment Control Mode>

In mines where the dump trucks are traveling, there is an increasingrequest for the reduction of the time necessary for transporting earth,sand, etc. This is because the reduction of the necessary time shortensthe earth/sand transportation cycle of each dump truck and increases thenumber of times of transportation. The vehicle speed is the major factordirectly contributing to the reduction of the necessary time. Therefore,it is desirable to avoid control that causes a decrease in the vehiclespeed.

FIG. 9 is a graph showing the effect of a method implementing the yawmoment correction value by a driving force difference on the totaldriving force of the motors when the vehicle is traveling with its 100%motor driving force. For example, assuming that the vehicle is currentlytraveling at a constant speed with its 100% driving force as shown onthe left side “a” of FIG. 9, the total driving force of the vehicle isin balance with the traveling resistance (air resistance, frictionalresistance, slope angle, etc.). In the configuration of this embodiment,the “100% driving force” means the output limits of the rear wheelmotors, that is, the maximum value of the driving force that the motorscan output at that speed. Let us consider here the method of generatingthe yaw moment by giving driving/braking force to the vehicle. In thiscase, the generation of the yaw moment can only be achieved bydecreasing the driving force of one of the right and left motors asshown on the right side “b” of FIG. 9 since the motors are already attheir output limits as mentioned above. While a yaw moment correspondingto the decrease in the driving force is generated in the vehicle, thevehicle speed drops due to the decrease in the driving force. This goesagainst the aforementioned request for the time reduction. Therefore,the actuator that should generate the yaw moment in this case is desiredto operate in a way not causing a considerable speed drop. Thus, settingthe yaw moment control mode to the mode 1 as shown in FIG. 8 isappropriate in this case. In contrast, when the driving force of thevehicle is below 100%, the yaw moment control mode is switched to themotor torque control (yaw moment control mode 2) or the optimumdistribution control (yaw moment control mode 3) depending on themagnitude of the driving force and other vehicle state quantities.

<Combining of Motor Torque Generated by Each Unit>

A method for the calculation of the motor torque command values by thecontroller 100 will be explained referring to FIG. 10. FIG. 10 is aschematic diagram showing an example of the method for calculating themotor torque command values. First, a processing unit 100 a selects theaforementioned torque command values T_MR_a and T_ML_a corresponding tothe driver's operation on the accelerator/retarder pedals or the torquecommand values T_MR_V and T_ML_V generated by the vehicle speed control.For example, the processing unit 100 a selects the driver's torquecommand when it exists. Otherwise, the processing unit 100 a selects thetorque command for the vehicle speed control. Thereafter, a calculationunit 100 b calculates motor torque command values T_MR and T_ML byadding the motor torque correction values T_MR_Y and T_ML_Ycorresponding to the yaw moment command value generated by the yawmoment control unit 102 respectively to the torque command valuesselected by the processing unit 100 a. This motor torque combiningmethod is just an example; various other methods (e.g. publicly-knownmethods) may be used.

<Overall Configuration of Characteristic Part>

Next, the overall configuration of the characteristic part of theelectrically driven dump truck in accordance with this embodiment willbe explained below referring to FIG. 11.

As mentioned above, the drive system of the electrically driven dumptruck of this embodiment includes the trolley wire detecting device 15for detecting the trolley wires 3R and 3L and the vehicle control device50.

The trolley wire detecting device 15 can be implemented typically by asensor such as a laser radar, a millimeter wave radar or a camera. In anX-Y plane formed by an X-axis representing the traveling direction ofthe vehicle (direction of the vehicle axis) and a Y-axis representingthe lateral direction (perpendicular to the vehicle axis) of thevehicle, any one of the above sensors serves in the present invention asmeans for detecting the relative positional relationship between thevehicle and the trolley wires. In the case of the laser radar, scanning(searching for the trolley wires) in the X-axis direction of the vehicleis effective for precisely detecting the trolley wires. In the case ofthe millimeter wave radar, ill effect of the weather (fog, rain, etc.)is lighter in comparison with other types of sensors. These radarsensors are capable of detection not only in the XY directions but alsoin the Z direction (height direction of the vehicle and the trolleywires). Therefore, the radar sensors can be suitable in cases where thesystem of the present invention is used together with a system needingthe detection in the height direction.

In the case of the camera, images of the trolley wires are shot frombelow, and thus the trolley wires can be detected precisely in thedaytime with fine weather thanks to high contrast between the sky andthe trolley wires. It is also possible to equip the vehicle 1 with anilluminating device 51 for illuminating the trolley wires 3R and 3L(claim 9). In this case, the illumination of the trolley wires 3R and 3Lwith the illuminating device 51 keeps high contrast between the sky andthe trolley wires, by which the trolley wires can be detected preciselyeven when such high contrast is hardly achieved (evening, nighttime,rainy weather, etc.).

The system may also be constructed by combining two or more sensors.

FIG. 11 is a schematic diagram showing the configuration of the vehiclecontrol device 50 and the input-output relationship between the vehiclecontrol device 50 and the controller 100. As shown in FIG. 11, thevehicle control device 50 includes a trolley wire detection informationprocessing unit 50 a, a vehicle state quantity calculation unit 50 b,and a vehicle state quantity control unit 50 c. The trolley wiredetection information processing unit 50 a acquires information on therelative positional relationship between the vehicle and the trolleywires by processing information detected by the trolley wire detectingdevice 15. The vehicle state quantity calculation unit 50 b calculatesstate quantities of the vehicle based on the information acquired by thetrolley wire detection information processing unit 50 a. The vehiclestate quantity control unit 50 c controls the vehicle state quantitiesbased on the result of the calculation by the vehicle state quantitycalculation unit 50 b. The trolley wires 3R and 3L are supported bysupports 53 via insulators 52. The vehicle control device 50 outputs atarget speed correction value, the yaw moment correction value, the yawmoment control mode, the elevation control device elevation command,control/detection state information, etc.

In this embodiment, the explanation of the detection of the trolleywires will be given of a case where a camera is used as the trolley wiredetecting device 15 and the relative positional relationship between thevehicle and the trolley wires in the X-Y plane is detected by performingimage processing. Thus, the trolley wire detecting device 15 isimplemented by a camera and the trolley wire detection informationprocessing unit 50 a is implemented by an image information processingunit which processes the image information captured by the camera 15.

<Camera 15 and Image Information Processing Unit 50 a>

The camera 15 captures images of the trolley wires 3R and 3L. In thiscase where the two trolley wires 3R and 3L are shot by one camera, thecamera 15 is desired to be placed at the center of the right and lefttrolley wires 3R and 3L. It is also possible to shoot each of the rightand left trolley wires 3R and 3L respectively with one camera. The imageinformation captured by the camera 15 is sent to the image informationprocessing unit 50 a of the vehicle control device 50. The imageinformation represents pixel arrangement in the area shot by the camera15. The image information processing unit 50 a converts the imageinformation into necessary information.

When a strong light source exists in the shooting direction of thecamera 15, a whitening and blurring effect called “halation” can occurto the image inputted to the image information processing unit 50 a andthis can disable the recognition of the target of detection. As acountermeasure against this problem, it is possible to use two cameras:one for shooting the trolley wires 3R and 3L in front of the vehicle andanother for shooting the trolley wires 3R and 3L in back of the vehicle.When the image information processing unit 50 a judges that the halationhas occurred in an image captured by one camera, a correction can bemade by use of the other camera. The halation can be detected accordingto publicly known methods. The two-camera configuration is effective notonly when the halation occurs but also when the visual field of onecamera is blocked. When the image information processing unit 50 ajudges that the visual field of one camera is blocked by dirt, mud,etc., a correction can be made similarly by using the other camera. Itis also possible to enclose the camera 15 with a housing, make thecamera 15 shoot the trolley wires 3R and 3L through glass of thehousing, and wash the glass with a wiper, washer fluid, etc. when theimage information processing unit 50 a judges that the visibilitythrough the glass has been deteriorated by dirt, mud, etc.

When the image information processing unit 50 a judges that the amountof ambient light is insufficient for the detection of the trolley wires3R and 3L (twilight, darkness, etc.), the image information processingunit 50 a may output a blink command to the illuminating device 51 tomake the illuminating device 51 illuminate the trolley wires 3R and 3Land maintain high contrast between the sky and the trolley wires.

In this embodiment, a case where the camera 15 captures images in thedirection directly above the vehicle as shown in FIG. 12 (not in theoblique direction as shown in FIG. 11) will be considered for thesimplicity of the explanation. In this case, an imaging area a, b, c, dof the camera 15 (detecting area of the trolley wire detecting device)is set in front of the vehicle as shown in FIG. 13. FIG. 14 is aschematic diagram showing an image captured by the camera 15 in thiscase. Since the camera 15 has shot the image of the trolley wires 3R and3L from below in FIG. 14, the anteroposterior relationship among thepoints a, b, c and d (positional relationship between the line a−d andthe line b−c) and the traveling direction of the vehicle are opposite tothose in FIG. 13 in which the trolley wires 3R and 3L are viewed fromabove.

As shown in FIG. 14, in the image information acquired by the camera 15,the trolley wires 3R and 3L appear in parallel with the travelingdirection (in the vertical direction in the image). On this imageinformation, a process for extracting edge parts (edging process) isperformed as shown in FIG. 15. By the edging process, the right trolleywire 3R is split into edges RR and RL, while the left trolley wire 3L issplit into edges LR and LL. Subsequently, as shown in FIG. 16, a centerline of the edges is determined for each of the right and left trolleywires 3R and 3L (a center line RM for the right trolley wire 3R and acenter line LM for the left trolley wire 3L). Then, a coordinate systemin regard to the pixel number is set with its origin situated at the topcenter Oc of the image (with its X-axis extending in the directionparallel to the line ab and its Y-axis extending in the directionparallel to the line da). Subsequently, the intersection point P (0,M_Lad_Ref) of the center line LM and the line ad, the intersection pointQ (0, M_Rad_Ref) of the center line RM and the line ad, the intersectionpoint R (m, M_Lbc_Ref) of the center line LM and the line bc, and theintersection point S (m, M_Rbc_Ref) of the center line RM and the linebc are set with respect to the origin Oc. These points P, Q, R and S,existing on the trolley wires 3R and 3L, are defined as target points.Incidentally, the number “m” represents the number of pixels in thevertical direction and the number “n” represents the number of pixels inthe horizontal direction.

If each trolley wire 3R, 3L is situated at the center of each slider4Ra, 4La when the vehicle is traveling straight at the center of the twotrolley wires 3R and 3L and in parallel with the trolley wires 3R and3L, this serves as robustness against deviations (displacement) causedby lateral (right/left) misalignment and vibration (jolting) of thevehicle. Therefore, the vehicle is desired to keep on traveling in sucha state.

FIG. 17 shows a state in which the vehicle has shifted to the left. Bysetting representative points of the vehicle 1 at intersection points oflines parallel to the X-axis (i.e., in the traveling direction of thevehicle 1) and passing through the center of the slider 4Ra or 4La andthe lines ad and be of the imaging area, the points P′, Q′, R′ and S′shown in FIG. 17 are acquired as the representative points. Theserepresentative points are points used for controlling the position ofthe vehicle with respect to the trolley wires 3R and 3L. Therefore, therepresentative points P′, Q′, R′ and S′ can also be referred to ascontrol points. Coordinates of these representative points are definedas M_Lad_Cont, M_Rad_Cont, M_Lbc_Cont and M_Rbc_Cont, respectively.

FIG. 18 shows a case where the vehicle is traveling obliquely to thetrolley wires 3R and 3L. Also in this case, the representative points ofthe vehicle are defined as the points P′, Q′, R′ and S′.

The image information processing unit 50 a sends the coordinateinformation on these points to the vehicle state quantity calculationunit 50 b.

<Vehicle State Quantity Calculation Unit 50 b>

The vehicle state quantity calculation unit 50 b calculates deviationsbetween the representative points P′, Q′, R′ and S′ and the targetpoints P, Q, R and S. The deviations e_Lad, e_Rad, e_Lbc and e_Rbcbetween the representative points and the target points are calculatedas follows:e _(—) Lad=M _(—) Lad _(—) Ref−M _(—) Lad_Cont  (1)e _(—) Rad=M _(—) Rad _(—) Ref−M _(—) Rad_Cont  (2)e _(—) Lbc=M _(—) Lbc _(—) Ref−M _(—) Lbc_Cont  (3)e _(—) Rbc=M _(—) Rbc _(—) Ref−M _(—) Rbc_Cont  (4)

These deviations take on positive/negative values when the vehicle hasshifted leftward/rightward with respect to the trolley wires.

The displacement (deviation) is defined similarly also when the vehicleis traveling obliquely to the trolley wires 3R and 3L as shown in FIG.18. In this case, the inclination eθ_L of the vehicle with respect tothe left trolley wire 3L and the inclination eθ_R of the vehicle withrespect to the right trolley wire 3R can be calculated as follows:eθ _(—) L=(e _(—) Lbc−e _(—) Lad)/m  (5)eθ _(—) R=(e _(—) Rbc−e _(—) Rad)/m  (6)

When the camera is successfully detecting the right and left trolleywires 3R and 3L as in this embodiment, the expressions (2), (4) and (6)are redundant to the expressions (1), (3) and (5). Therefore, it isdesirable to perform the calculation by using information on asuccessful side (on which the displacement and the inclination can becalculated successfully) when the calculation of the displacement andthe inclination is impossible on one side for some reason.

<Vehicle State Quantity Control Unit 50 c>

Next, the vehicle state quantity control unit 50 c will be explainedbelow. The purpose of the vehicle state quantity control unit 50 c is tocalculate the yaw moment correction value which is used for making atleast one of the representative points coincide with the correspondingtarget point. A process for generating the yaw moment correction valueby multiplying the inclination and the displacement represented by theexpression (1) by gain factors is shown in FIG. 19. FIG. 19 is a blockdiagram showing the details of the function of the vehicle statequantity control unit 50 c. In this example, the point P or Q is used asthe target point and the point P′ or Q′ is used as the representativepoint.

As shown in FIG. 19, a calculation unit 50 c ₁ of the vehicle statequantity control unit 50 c determines the deviation e_Lad (e_Rad)between the representative point P′ (Q′) and the target point P (Q) bycalculating the difference between the coordinate value M_Lad_Cont(M_Rad_Cont) of the representative point P′ (Q′) and the coordinatevalue M_Lad_Ref (M_Rad_Ref) of the target point P (Q) inputted from thevehicle state quantity calculation unit 50 b. A conversion unit 50 c ₂of the vehicle state quantity control unit 50 c converts the deviatione_Lad (e_Rad) into a yaw moment value by multiplying the deviation by again factor. Meanwhile, a conversion unit 50 c ₃ converts theinclination eθ_L (eθ_R) of the vehicle inputted from the vehicle statequantity calculation unit 50 b into a yaw moment value by multiplyingthe inclination by a gain factor. A calculation unit 50 c ₄ calculatesthe yaw moment correction value by adding the two yaw moment valuestogether and outputs the calculated yaw moment correction value to theyaw moment control unit 102.

The vehicle state quantity control unit 50 c also determines the yawmoment control mode which has been explained referring to FIG. 8. Theaforementioned yaw moment control unit 102 of the controller 100calculates the motor torque command values and the steerage torquecorrection value based on the yaw moment correction value and the yawmoment control mode determined by the vehicle state quantity controlunit 50 c and then outputs the motor torque command values and thesteerage torque correction value to the inverter control device 30 andthe steering control device 32, respectively.

With the configuration and operation described above, the control device(made up of the vehicle control device 50, the controller 100, theinverter control device 30 and the steering control device 32) executescontrol to give an appropriate yaw moment to the vehicle 1 so that thevehicle 1 travels while tracing the trolley wires 3R and 3L (claim 1).In this case, the control device carries out control to give anappropriate yaw moment to the vehicle 1 so that the representative pointP′ (Q′) approaches the target point P (Q) (claim 2). Further, thecontrol device carries out control to give an appropriate yaw moment tothe vehicle 1 so that the inclination eθ_L decreases (claim 3).

Besides the simple gain control shown in FIG. 19, integral control,derivative control, etc. may also be employed.

<Effect>

According to this embodiment configured as above, the following effectsare achieved: Since the trolley wires 3R and 3L are detected from belowin this embodiment, there are less factors leading to detection errorscompared to the conventional technique detecting lane markers, etc. bycapturing images of the ground surface. As a result, the accuracy of thetrolley wire detection is improved. Thanks to the improvement of thetrolley wire detection accuracy, the control accuracy of the yaw momentcontrol for making the vehicle travel while tracing the trolley wires 3Rand 3L is improved and the central position of each slider 4Ra/4La ofthe traveling vehicle hardly deviates widely from the trolley wire 3R/3Lin the lateral direction. Consequently, the operating load on the driverin the trolley traveling section can be lightened considerably.

In the case where a camera 15 is used as the trolley wire detectingdevice, illuminating the trolley wires 3R and 3L with the illuminatingdevice 51 is effective for maintaining high contrast between the sky andthe trolley wires 3R and 3L. By use of the illuminating device 51, theyaw moment control for making the vehicle travel while tracing thetrolley wires 3R and 3L can be executed with high accuracy not only inthe daytime with fine weather but also in conditions in which such highcontrast between the sky and the trolley wires 3R and 3L is hardlyachieved (evening, nighttime, rainy weather, etc.).

Furthermore, the control device 200 is capable of executing the yawmoment control by using the vehicle control device 50 and the controller100 as separate components. With this configuration, even when thecontroller 100 is an already-existing controller, the yaw moment controlin accordance with the present invention can be carried out by justadding the vehicle control device 50 to the controller. The parametersof the yaw moment control can be adjusted just by changing the functionsof the vehicle control device 50. Consequently, high flexibility can begiven to the control system.

<Another Embodiment of Vehicle Control Device 50>

Next, another embodiment of the vehicle control device 50 will bedescribed below.

The main difference between this embodiment and the above embodiment isas follows: In the above embodiment, only the control for giving anappropriate yaw moment to the vehicle 1 to make the vehicle travel whiletracing the trolley wires 3R and 3L (hereinafter referred to as “trolleywire tracing control”) was executed. In this embodiment, elevationcontrol of the sliders 4Ra and 4La of the power collectors 4R and 4L isexecuted in addition to the trolley wire tracing control. In the trolleywire tracing control, a dead zone is set in regard to the deviationbetween the representative point and the target point. The trolley wiretracing control is carried out only when the deviation has exceeded thedead zone.

<Image Information Processing Unit 50 a>

The image information processing unit 50 a executes the same process asthat in the above embodiment and sends coordinate information on therepresentative points P′, Q′, R′ and S′ to the vehicle state quantitycalculation unit 50 b.

<Vehicle State Quantity Calculation Unit 50 b and Vehicle State QuantityControl Unit 50 c>

The vehicle state quantity calculation unit 50 b calculates statequantities to be used for generating control values and command valuessuch as the yaw moment correction value for the trolley wire tracingcontrol, the elevation control device elevation command for the sliderelevation control, the yaw moment control mode and the target speedcorrection value. The vehicle state quantity control unit 50 c generatesand outputs the control values and the command values (the yaw momentcorrection value, the elevation control device elevation command, theyaw moment control mode, the target speed correction value, etc.) basedon the result of the calculation by the vehicle state quantitycalculation unit 50 b.

<Trolley Wire Detecting Area and Coordinate System>

First, a trolley wire detecting area and a coordinate system used by thevehicle state quantity calculation unit 50 b in this embodiment will beexplained below.

FIG. 20 is a schematic diagram showing the trolley wire detecting areaand the coordinate system used in this embodiment.

From the image information on the imaging area a, b, c, d (see FIGS.16-18) acquired by the image information processing unit 50 a from thecamera 15, the vehicle state quantity calculation unit 50 b extracts andacquires an area like the area a1, b1, c1, d1 shown in FIG. 20 as thetrolley wire detecting area. The side a1-d1 corresponds to a part of theside a-d of the imaging area a, b, c, d shown in FIGS. 16-18, while theside b1-c1 corresponds to a part of the side b-c of the imaging area a,b, c, d. The trolley wire detecting area a1, b1, c1, d1 indicates thepositional relationship between the slider and the trolley wire 3R or 3Lwhen the trolley wire 3R/3L is viewed from above. In the trolley wiredetecting area a1, b1, c1, d1, a straight line passing through thecenter of the slider 4Ra/4La (regarding the lateral direction) andextending in the traveling direction of the vehicle passes through thecenter of the side a1-d1 and the center of the side b1-c1. As mentionedabove, since the trolley wires 3R and 3L are shot from below in theimage information on the imaging area a, b, c, d acquired by the camera15, the anteroposterior relationship (vertical direction in FIG. 19) inthe trolley wire detecting area a1, b1, c1, d1 (viewing the trolley wire3R/3L from above) is opposite to that in the imaging area a, b, c, d.

Further, the vehicle state quantity calculation unit 50 b sets acoordinate system having the origin (Op) at the center of the slider4Ra/4La, the X-axis extending in the traveling direction, and the Y-axisextending leftward with respect to the traveling direction. In thecoordinate system, the vehicle state quantity calculation unit 50 b setsa representative point at the intersection point Z of the X-axis and theside b1-c1, and sets two target points at the intersection point T ofthe trolley wire 3R/3L and the side b1-c1 and at the intersection pointU of the trolley wire 3R/3L and the side a1-d1. Since the camera 15 andthe slider 4Ra/4La of the power collector 4R/4L are both attached to thevehicle and the positional relationship between the two components arealready known, the coordinates of the intersection points Z, T and U canbe determined with ease by means of coordinate transformation, bytransforming coordinate values of the points P′, P and R in thecoordinate system with the origin Oc shown in FIGS. 16-18 intocoordinate values in the coordinate system with the origin Op shown inFIG. 20.

<Trolley Wire Tracing Control>

The vehicle state quantity calculation unit 50 b calculates thedeviation between the representative point Z and the target point T.Since the Y-coordinate value Y_Cbc of the target point T in front of theslider 4Ra/4La equals the deviation between the representative point Zand the target point T, the vehicle state quantity calculation unit 50 buses the Y-coordinate value Y_Cbc of the target point T as the deviationbetween the representative point Z and the target point T. The deviationY_Cbc takes on a positive/negative value when the vehicle has shiftedrightward/leftward with respect to the trolley wires.

When the vehicle is traveling obliquely to the trolley wire 3R/3L,similar displacement is defined also in regard to the inclination of thevehicle. In this case, the inclination θ_t of the vehicle with respectto the trolley wire 3R/3L at a certain time t is represented by thefollowing expression by using the coordinate values of the two targetpoints T and U:θ_(—) t=(Y _(—) Cbc−Y _(—) Cad)/(X _(—) Cbc−X _(—) Cad)  (7)

The vehicle state quantity control unit 50 c calculates the yaw momentcorrection value (for making the representative point Z coincide withthe target point T) by using the deviation Y_Cbc between therepresentative point Z and the target point T or the inclination θ_t ofthe vehicle.

A process for calculating the yaw moment correction value by using thedeviation Y_Cbc or the inclination θ_t is shown in FIG. 23B. FIG. 23B isa block diagram similar to FIG. 19, showing an example of a method forcalculating the yaw moment correction value. As mentioned above, theY-coordinate value Y_Cbc of the target point T in front of the slider4Ra/4La equals the deviation between the representative point Z and thetarget point T. This deviation Y_Cbc corresponds to the deviation e_Ladbetween the representative point P′ and the target point P calculated bythe calculation unit 50 c ₁ shown in FIG. 19. Therefore, the calculationunit 50 c ₁ is not provided in the block diagram of FIG. 23B. Theconversion unit 50 c ₂ of the vehicle state quantity control unit 50 cconverts the deviation Y_Cbc into a yaw moment value by multiplying thedeviation Y_Cbc by a gain factor. Meanwhile, the conversion unit 50 c ₃converts the inclination θt into a yaw moment value by multiplying theinclination θt by a gain factor. The calculation unit 50 c ₄ calculatesthe yaw moment correction value by adding the two yaw moment valuestogether and outputs the calculated yaw moment correction value to theyaw moment control unit 102.

The other functions of the vehicle state quantity control unit 50 crelated to the trolley wire tracing control are equivalent to those inthe first embodiment.

<Slider Elevation Control>

The vehicle state quantity calculation unit 50 b calculates theinclination θ_t of the vehicle at a certain time t. As mentioned above,this inclination θ_t can be calculated according to the above expression(7) by using the coordinate values of the two target points T and Ushown in FIG. 20.

Further, the vehicle state quantity calculation unit 50 b calculates theY-coordinate (Y_p_t) of a point W which is defined as the intersectionpoint of the slider 4Ra/4La and the trolley wire 3R/3L.

The Y-coordinate Y_p_t of the point W can be approximated as follows:Y _(—) p _(—) t=Y _(—) Cbc−θ _(—) t×X _(—) Cbc orY _(—) p _(—) t=Y _(—) Cad−θt×X _(—) Cad  (8)

Here, Y_P_t+1 as the value of Y_p_t one step later (after a timeinterval Δ) is expressed by using the vehicle speed V as follows:Y _(—) p _(—) t+1=Y _(—) p _(—) t+V×tan θ _(—) t  (9)

Assuming that the permissible range of the Y-coordinate Y_p_t of thepoint W on the slider 4Ra/4La, within which the slider 4Ra/4La is incontact with the trolley wire 3R/3L and satisfactory electric power canbe acquired continuously, is Y_min (Y-coordinate of a pointD)<Y_p_t<Y_max (Y-coordinate of a point C) between points C and D, itcan be said that there is no problem with elevating the slider 4Ra/4Lain a range satisfying Y_min<Y_p_t+1<Y_max.

At the present time t, the vehicle state quantity calculation unit 50 bjudges whether or not the Y-coordinate Y_p_t of the point W will beoutside the range between Y_min (Y-coordinate of the point D) and Y_max(Y-coordinate of the point C) in the next control step t+1, and outputsthe result of the judgment to the vehicle state quantity control unit 50c. If the Y-coordinate Y_p_t of the point W will be outside the rangebetween Y_min (Y-coordinate of the point D) and Y_max (Y-coordinate ofthe point C), the vehicle state quantity control unit 50 c outputs acommand signal for lowering the sliders 4Ra and 4La or prohibiting theelevation of the sliders 4Ra and 4La. In contrast, if the Y-coordinateY_p_t will be within the range, the vehicle state quantity control unit50 c outputs a command signal for elevating the sliders 4Ra and 4La orpermitting the elevation of the sliders 4Ra and 4La. The vehicle statequantity control unit 50 c may also correct the reaction force of thereaction force motor 42 (see FIG. 5) of the steering device 40 dependingon the Y-coordinate Y_p_t of the point W. For example, the correctionmay be made to decrease the reaction force in the range satisfyingY_min<Y_p_t+1<Y_max and to increase the reaction force in the rangessatisfying Y_p_t+1≦Y_min or Y_max≦Y_p_t+1.

In this example, the vehicle control device 50 is executing both thetrolley wire tracing control and the slider elevation control. In thetrolley wire tracing control, the vehicle state quantity control unit 50c outputs the yaw moment correction value calculated by multiplying thedeviation Y_Cbc or the inclination θ_t by a gain factor. Since theoutputting of the yaw moment correction value continues until thedeviation Y_Cbc or the inclination θ_t becomes 0, the Y-coordinate Y_p_tof the point W on the slider 4Ra/4La and the inclination θ_t of thevehicle tend to converge on 0 eventually.

<Details of Control Process by Vehicle Control Device 50>

The details of the control process executed by the vehicle controldevice 50, including the aforementioned elevation control of the sliders4Ra and 4La, will be explained below referring to a flow chart of FIG.21. FIG. 21 is a flow chart showing the flow of the process from theupward shooting with the camera to the control output. It is assumed asshown in FIG. 12 that a camera is set in front of the vehicle 1 to be onthe extension line of the vehicle axis and the number of trolley wiresshot with the camera is one. FIG. 22 is a schematic diagram similar toFIG. 20, wherein a dead zone of the trolley wire tracing control hasbeen set. The target points T and U and the representative point Z havebeen set for the detecting area a1, b1, c1, d1 as explained above.Further, points A and B specifying the dead zone of the trolley wiretracing control have been set at positions a prescribed distance (firstthreshold value) apart (Y_l, Y_r) from the representative point Z.

In the first step 200, the image information processing unit 50 acaptures an image upward from the vehicle 1 with the camera. In step201, the image information processing unit 50 a searches the capturedimage for the trolley wire 3R/3L. In the search in the step 201, thewhole area of the captured image is searched when the detection of thetrolley wire 3R/3L is carried out for the first time. After the trolleywire 3R/3L has been detected once, searching the whole area isunnecessary; searching only a limited area in the vicinity of thecoordinates of the already detected trolley wire 3R/3L is effectivesince it leads to reduction of the search time. In step 202, the imageinformation processing unit 50 a judges whether or not there exists anobject corresponding to the trolley wire 3R/3L in the captured image. Ifno object corresponding to the trolley wire 3R/3L is found, the processis finished. If there exists an object corresponding to the trolley wire3R/3L, the process advances to step 203A. In the step 203A, the imageinformation processing unit 50 a executes the edge extraction and theimage processing for calculating the center line of the trolley wire3R/3L.

Thereafter, the process is handed over to the vehicle state quantitycalculation unit 50 b. In step 203B, the vehicle state quantitycalculation unit 50 b sets the aforementioned target points T and U andcalculates the coordinates of the target points T and U. At this point,the process using the coordinate information on the target points T andU separates into two flows: a tracing control step 300 for tracing thetrolley wire 3R/3L and an elevation control step 400 for controlling theelevation of the slider 4Ra/4La.

<Trolley Wire Tracing Control>

First, the trolley wire tracing control step 300 will be explainedbelow.

In step 310, the vehicle state quantity calculation unit 50 b judgeswhether or not the target point T exists between the points A and B(Y_l≦Y_Cbc, Y_r≧Y_Cbc) which have been set at positions a prescribeddistance apart (Y_l, Y_r) from the representative point Z shown in FIG.22. When the target point T does not exist between the points A and B,the process advances to step 320 and the vehicle state quantity controlunit 50 c calculates and outputs the yaw moment correction value.

FIG. 23A is a schematic diagram showing an example of a method forcalculating the yaw moment correction value employed in this case. InFIG. 23A, the gradient of the characteristic lines outside the points Aand B corresponds to the gain of the conversion unit 50 c ₂ in FIG. 23B(conversion unit 50 c ₂ in FIG. 19).

As shown in FIG. 23A, a yaw moment correction value corresponding to theY-coordinate value Y_Cbc of the target point T (corresponding to thedeviation between the representative point Z and the target point T) iscalculated outside the points A and B. Specifically, in the rangeoutside the point A (where Y_Cbc is positive), the yaw moment correctionvalue is increased with the increase in Y_Cbc. In the range outside thepoint B (where Y_Cbc is negative), the yaw moment correction value isdecreased with the decrease in Y_Cbc. According to this calculation,when the target point T does not exist between the points A and B (i.e.,when the absolute value of the deviation Y_Cbc between therepresentative point Z and the target point T is greater than theabsolute value of the Y-coordinate value Y_l of the point A or theY-coordinate value Y_r of the point B as the first threshold value),control is executed to give an appropriate yaw moment to the vehicle 1so as to make the representative point Z approach the target point T(claim 4). Further, the control is executed so that the yaw moment givento the vehicle 1 increases with the increase in the absolute value ofthe deviation Y_Cbc (claim 5). After the yaw moment correction value hasreached a maximum correction value or a minimum correction value, theyaw moment correction value is set constant in order to preventabrupt/extreme turning of the vehicle. Incidentally, it is also possibleto output a constant yaw moment correction value in such cases where thetarget point T does not exist between the points A and B, instead ofcalculating and outputting the yaw moment correction value as avariable.

Here, the reason for setting the yaw moment correction value at 0between the points A and B shown in FIG. 23 will be explained (claim 4).By the control for making the representative point Z coincide with thetarget point T, the point W is positioned almost at the center of theslider 4Ra/4La as long as the vehicle 1 is traveling forward. In thiscase, however, the yaw moment correction value is calculated even whenthe point W has slightly shifted from the center of the slider 4Ra/4Laand that increases the frequency of operation of the actuatorsimplementing the yaw moment correction (the reaction force motor 42 andthe steerage motor 43 of the steering device 40 (FIG. 5) and the rearwheel electric motors 6R and 6L (FIG. 3) in this embodiment). By settingthe yaw moment correction value at 0 between the points A and B, thefrequency of operation of the rear wheel electric motors 6R and 6L canbe reduced and high control stability and riding comfort can be secured.The width of the range between the points A and B (in which the yawmoment correction is unnecessary) may be set depending on the width ofthe slider 4Ra/4La.

Further, by executing the control so as to increase the yaw moment givento the vehicle 1 with the increase in the absolute value of thedeviation Y_Cbc (claim 5), the vehicle 1 is given the yaw moment so thattrolley wires 3R and 3L quickly return to the center of the sliders 4Raand 4La when the slider 4Ra/4La of the traveling vehicle is about towidely deviate from the trolley wire 3R/3L in the lateral direction.Consequently, the dump truck can securely be prevented from deviatingfrom the lane with the trolley wires 3R and 3L.

In the next step 330, the yaw moment control mode is selected andoutputted. In normal traveling, the mode “1” is selected as the yawmoment control mode since there is no request for reducing the vehiclespeed (driver's retarder operation or deceleration by other control).

<Another Example of Trolley Wire Tracing Control>

Next, another example of the trolley wire tracing control will beexplained below referring to FIGS. 24-27. FIG. 24 is a schematic diagramsimilar to FIGS. 20 and 22, wherein deviation monitoring points for thetrolley wire tracing control have been set. FIG. 25 is a flow chartshowing step 300′ which is executed instead of the trolley wire tracingcontrol step 300 in the flow chart of FIG. 21.

As shown in FIG. 24, a point A′ (second threshold value) at a positionoutside (with a larger Y-coordinate value than) the point A and with aY-coordinate value Y_l′ and a point B′ (second threshold value) at aposition outside (with a smaller negative Y-coordinate value than) thepoint B and with a Y-coordinate value Y_r′ have been set as thedeviation monitoring points for the trolley wire tracing control.

In FIG. 25, the process till the step 320 for calculating the yaw momentcorrection value is identical with that in FIG. 21 explained above. Instep 321 after the step 320, whether the target point T is situatedbetween the points A′ and B′ (Y_l′≦Y_Cbc, Y_r′≦Y_Cbc) or not is judged(step 321). If affirmative, a warning for urging the driver to correctthe steering is issued by sound and/or display (step 322) since there isa possibility that the vehicle deviates from the trolley lane (claim 6).

In the next step 323, the target vehicle speed is corrected depending onthe position of the target point T. FIG. 26 is a schematic diagramshowing an example of a method for calculating a target vehicle speedcorrection value in this case. As shown in FIG. 26, when the targetpoint T does not exist between the points A′ and B′, the target vehiclespeed correction value is calculated so as to reduce the target vehiclespeed depending on the degree of deviation from the points A′ and B′.Specifically, in the range outside the point A′ (where Y_Cbc ispositive), the correction value on the side of decreasing the targetvehicle speed is increased with the increase in Y_Cbc. In the rangeoutside the point B′ (where Y_Cbc is negative), the correction value onthe side of decreasing the target vehicle speed is decreased with thedecrease in Y_Cbc. According to this calculation, when the target pointT does not exist between the points A′ and B′ (i.e., when the absolutevalue of the deviation Y_Cbc between the representative point Z and thetarget point T is greater than the absolute value of the Y-coordinatevalue Y_l′ of the point A′ or the Y-coordinate value Y_r′ of the pointB′ as the second threshold value), control is executed to decrease thetraveling speed with the increase in the absolute value of the deviationY_Cbc. Decreasing the vehicle speed as above is effective for lighteningthe operating load on the driver and giving a feeling of security to thedriver.

FIG. 27 is a schematic diagram showing another example of the method forcalculating the target vehicle speed correction value. As shown in FIG.27, when the target point T exists between the points A′ and B′, thecorrection may be made to increase the target vehicle speed as targetpoint T approaches the representative point Z. Specifically, in therange inside the point A′ (where Y_Cbc is positive), the correctionvalue on the side of increasing the target vehicle speed is increasedwith the decrease in Y_Cbc. In the range inside the point B′ (whereY_Cbc is negative), the correction value on the side of increasing thetarget vehicle speed is decreased with the increase in Y_Cbc. Accordingto this calculation, when the target point T exists between the pointsA′ and B′ (i.e., when the absolute value of the deviation Y_Cbc betweenthe representative point Z and the target point T is less than theabsolute value of the Y-coordinate value Y_l′ of the point A′ or theY-coordinate value Y_r′ of the point B′ as the second threshold value),control is executed to increase the traveling speed with the decrease inthe absolute value of the deviation Y_Cbc. Increasing the vehicle speedas above is effective for increasing the working efficiency.

FIG. 28 is a schematic diagram similar to FIG. 10, showing a method forgenerating motor torque according to the target vehicle speed correctionvalue. As shown in FIG. 28, the target vehicle speed correction valuecalculated as above is converted into a motor torque correction value bya conversion unit 100 c by multiplying the target vehicle speedcorrection value by a gain factor. Subsequently, the motor torquecommand values T_MR and T_ML are calculated by a calculation unit 100 dby adding the motor torque correction value (corresponding to the targetvehicle speed correction value) calculated by the conversion unit 100 cto the motor torque command values calculated by the calculation unit100 b (acquired by adding the motor torque correction values T_MR_Y andT_ML_Y corresponding to the yaw moment command value generated by theyaw moment control unit 102 (FIG. 8) to the torque command valuesselected by the processing unit 100 a).

Next, the yaw moment control mode in the case where the target vehiclespeed is corrected to a lower value according to the target vehiclespeed correction value shown in FIG. 26 will be explained. As shown inFIG. 9, in cases where a yaw moment has to be generated when the rightand left motors are outputting 100% motor torque, it is necessary toreduce the motor torque of one of the right and left motors. Thereduction of the motor torque of one of the motors leads to a drop inthe vehicle speed since the vehicle cannot maintain the present speedwith the reduced motor torque. Thus, in cases where the target vehiclespeed is corrected to a lower value, the yaw moment correction may bemade not by the steerage torque correction but by the correction of themotor torque, by which both the control of giving a yaw moment to thevehicle 1 by controlling the right and left electric motors 6R and 6Land the control of the traveling speed are carried out (claim 7).Consequently, efficient control, achieving both the deceleration and thegeneration of the yaw moment at the same time, can be carried out.

<Slider Elevation Control>

Next, the slider elevation control step 400 will be explained below.

As shown in FIGS. 20, 22 and 24, the points C and D are set to specifythe permissible range of the Y-coordinate Y_p_t of the point W on theslider 4Ra/4La within which the slider 4Ra/4La is in contact with thetrolley wire 3R/3L and satisfactory electric power can be acquiredcontinuously.

In step 410 in FIG. 21, the inclination of the trolley wire 3R/3L iscalculated from the target points T and U according to the expression(7). From the inclination and the coordinates of the target point T, thecoordinates of the intersection point W of the slider 4Ra/4La and thetrolley wire 3R/3L is calculated in step 420. This calculation isperformed according to the aforementioned expression (8). In the nextstep 430, the estimate Y_p_t+1 of the Y-coordinate of the intersectionpoint W in the next step is calculated. In step 440, duration of a statein which the estimate Y_p_t+1 stays in the prescribed range between thepoints C and D (Y_min≦Y_p_t+1≦Y_max) is measured by use of a counter andwhether or not the duration of the state was a prescribed period (e.g.,1 second) or longer is judged. If the duration of the state (with thepoint W existing between the points C and D) was 1 second or longer inthe step 440, the process advances to step 450 and the elevation of thesliders 4Ra and 4La is permitted. In this case, it is possible, forexample, to inform the driver of the permission of the elevation of thesliders 4Ra and 4La by sound and/or display. In response to a switchingoperation by the driver, the vehicle control device 50 outputs a commandsignal for the elevation control and the elevation control device 31controls the elevation of the sliders 4Ra and 4La according to thecommand signal. When the sliders 4Ra and 4La have been lowered, it isalso possible to automatically elevate the sliders 4Ra and 4La, forexample, instead of entrusting the elevating operation to the driver.The vehicle control device 50 outputs the command signal for theelevation control and the elevation control device 31 controls theelevation of the sliders 4Ra and 4La according to the command signal. Inthis case, it is possible to inform the driver of the automaticelevation of the sliders 4Ra and 4La by sound and/or display, forexample.

In contrast, if the duration of the state (with the point W existing inthe prescribed range) was less than 1 second in the step 440, theprocess advances to step 460 to instruct the driver by sound and/ordisplay to lower the sliders 4Ra and 4La if the sliders have beenelevated. The sliders 4Ra and 4La may also be lowered automatically. Inthis case, it is desirable to inform the driver of the automaticlowering of the sliders 4Ra and 4La by sound and/or display, forexample. If the sliders 4Ra and 4La have already been lowered, theelevation of the sliders 4Ra and 4La is prohibited. In this case, it isdesirable to inform the driver of the prohibition of the elevation ofthe sliders 4Ra and 4La by sound and/or display. Also in these cases,the vehicle control device 50 outputs a command signal automatically orin response to the driver's switching operation and the elevationcontrol device 31 controls the lowering of the sliders 4Ra and 4Laaccording to the command signal. This lightens the load on the operator(driver) for elevating and lowering the sliders 4Ra and 4La after thedump truck has entered the trolley traveling section.

While the judgment on whether or not the state (in which the estimateY_p_t+1 stays between the points C and D (Y_min≦Y_p_t+1≦Y_max) continuedfor a prescribed period (e.g., 1 second) or longer is made in the step440 in FIG. 21, it is also possible to immediately advance to the step450 (without making such a judgment) when the estimate Y_p_t+1 existsbetween the points C and D (Y_min≦Y_p_t+1≦Y_max) and immediately advanceto the step 460 when the estimate Y_p_t+1 does not exist between thepoints C and D (Y_min≦Y_p_t+1≦Y_max). However, the step 440 is effectivefor the purpose of preventing the hunting of judgment caused by repeateddeviation/reentrance from/to the prescribed range when the Y-coordinateY_p_t of the point W is unstable due to undulation of the road surfaceand noise occurring in the image processing.

FIG. 29 is a schematic diagram showing a hysteresis process which can beexecuted instead of the step 440 employing the counter. As shown in FIG.29, when the point W exists between the points C and D, the setting ofthe points C and D is changed to increase the distance between thepoints C and D. In contrast, when the point W does not exist between thepoints C and D, the setting of the points C and D is changed to decreasethe distance between the points C and D. Also by giving hysteresis tothe distance between the points C and D as above, effect similar to thatof the counter process (step 440) can be achieved.

Other Examples

While the camera used as the trolley wire detecting device was pointeddirectly upward in the above embodiment, the camera may also be set tocapture images in a forward and upward direction from the vehicle asshown in FIG. 30. Such camera setting facilitates thedetection/recognition of the trolley wires as the target of the tracingsince the parts of the trolley wires shot with the camera in thevehicle's traveling direction are long. On the other hand, noise causedby the scenery included in the imaging area increases as the imagingarea is shifted forward. Therefore, the imaging area of the camera maybe adjusted properly depending on the environment in which the presentinvention is employed.

DESCRIPTION OF REFERENCE NUMERALS vehicle

-   1 vessel-   3L, 3R trolley wire-   4L, 4R power collector-   4La, 4Ra slider-   4 a hydraulic piston device-   4 b hydraulic piston-   4 c rod-   4 d hydraulic line-   4 e hydraulic device-   4 f insulator-   4 g electric wire-   4 h elevation command signal-   5L, 5R rear wheel-   6L, 6R electric motor-   6La, 6Ra output shaft-   7L, 7R decelerator-   11 accelerator pedal-   12 retarder pedal-   13 shift lever-   14 combined sensor-   15 camera-   16L, 16R electromagnetic pickup sensor-   21 engine-   21 a electronic governor-   22 AC generator-   23 rectifier circuit-   24 sensing resistor-   25 capacitor-   26 chopper circuit-   27 grid resistor-   28 other engine load-   30 inverter control device-   30 a torque command calculation unit-   30 b motor control calculation unit-   30 c inverter (switching element)-   31 elevation control device-   32 steering control device-   32 a conversion unit-   32 b calculation unit-   32 c conversion unit-   32 d calculation unit-   40 steering device-   41 steering wheel-   42 reaction force motor having a steering angle sensor-   43 steerage motor having a steerage angle sensor-   44 rack-and-pinion gear-   45L, 45R front wheel-   50 vehicle control device-   50 a image information processing unit-   50 b vehicle state quantity calculation unit-   50 c vehicle state quantity control unit-   50 c ₁ calculation unit-   50 c ₂ conversion unit-   50 c ₃ conversion unit-   50 c ₄ calculation unit-   51 illuminating device-   52 insulator-   53 support-   100 controller-   100 a processing unit-   100 b calculation unit-   101 vehicle speed control unit-   101 a calculation unit-   101 b conversion unit-   101 c switch unit-   101 d zero output unit-   102 yaw moment control unit-   102 a calculation unit-   102 b steering torque control unit-   102 c motor torque control unit-   102 d optimum distribution control unit-   102 e switch unit-   200 control device-   P, Q, R, S target point-   P′, Q′, R′, S′ representative point-   T target point-   Z representative point (control point)-   e_Lad deviation-   θ_L inclination-   Y_Cbc deviation-   θ_t inclination-   Y_l, Y_r Y-coordinate value of point A, B (first threshold value)-   Y_I′, Y_r′ Y-coordinate value of point A′, B′ (second threshold    value)

The invention claimed is:
 1. An electrically driven vehicle whichelevates a slider of a power collector provided on the vehicle to bemovable up and down, places the slider in contact with a trolley wireinstalled along a lane, and travels by using electric power from thetrolley wire, comprising: a trolley wire detecting device which isprovided on the vehicle and detects the trolley wire from below when thevehicle is traveling; and a control device which executes control togive a yaw moment to the vehicle so that the vehicle travels whiletracing the trolley wire based on information detected by the trolleywire detecting device, wherein the control device calculates at leastone representative point of the vehicle and at least one target pointsituated on the trolley wire based on the information detected by thetrolley wire detecting device, and executes control to give a yaw momentto the vehicle so that the representative point approaches the targetpoint.
 2. The electrically driven vehicle according to claim 1, whereinthe control device calculates inclination of the vehicle with respect tothe trolley wire based on the information detected by the trolley wiredetecting device and executes control to give a yaw moment to thevehicle so that the inclination decreases.
 3. The electrically drivenvehicle according to claim 1, wherein the control device calculates adeviation between the representative point and the target point andexecutes the control to give a yaw moment to the vehicle so that therepresentative point approaches the target point when the absolute valueof the deviation is greater than a first threshold value.
 4. Theelectrically driven vehicle according to claim 1, wherein the controldevice calculates a deviation between the representative point and thetarget point and issues a warning that the vehicle is apt to deviatefrom the lane when the absolute value of the deviation is greater than asecond threshold value.
 5. The electrically driven vehicle according toclaim 1, further comprising right and left electric motors fortraveling, wherein the control device executes both the control to givea yaw moment to the vehicle and traveling speed control by controllingthe right and left electric motors.
 6. The electrically driven vehicleaccording to claim 1, further comprising right and left electric motorsfor traveling and a steering device, wherein: the control deviceincludes a vehicle control device, a controller, an inverter controldevice and a steering control device, and the vehicle control devicecalculates a yaw moment correction value, for the control to give a yawmoment to the vehicle so that the vehicle travels while tracing thetrolley wire, based on the information detected by the trolley wiredetecting device, and the controller controls at least the right andleft electric motors or the steering device by using the invertercontrol device and/or the steering control device based on the yawmoment correction value.
 7. The electrically driven vehicle according toclaim 1, wherein the trolley wire detecting device includes: a camerawhich is provided on the vehicle and continuously captures images of thetrolley wire when the vehicle is traveling; and an illuminating devicewhich is provided on the vehicle and illuminates the trolley wire. 8.The electrically driven vehicle according to claim 3, wherein thecontrol device increases the yaw moment given to the vehicle with theincrease in the absolute value of the deviation when the absolute valueis greater than the first threshold value.